RESUMO
We evaluated the physiological characteristics of chemical-tolerant cladocerans. Over the course of 26 generations (F25), Daphnia magna was continuously exposed to pirimicarb (carbamate) solutions (0, 3.8, 7.5, and 15 µg/L) in sub-lethal or lethal levels. The 48 h EC50 values (29.2-29.9 µg/L) for 7.5 and 15 µg/L exposure groups were found to be nearly two times higher than that in the control (17.2 µg/L). Subsequently, we investigated whether the extinction probability changed when the chemical-tolerant daphnids were fed two different types of food, Chlorella vulgaris and Synechococcus leopoliensis. Furthermore, we ascertained how chemical tolerance influences respiration and depuration rates. The 48 h EC50 value was positively related to the extinction probability when the daphnids were fed S. leopoliensis. Because the measured lipid content of S. leopoliensis was three times lower than that of C. vulgaris, the tolerant daphnids struggled under nutrient-poor conditions. Respiration rates across all pirimicarb treatment groups were higher than those in the control group, suggesting that they may produce large amounts of energy through respiration to maintain the chemical tolerance. Since the pirimicarb depuration rate for 7.5 µg/L exposure groups was higher than that in the control, the altered metabolic/excretion rate may be one factor for acquiring chemical tolerance. These altered physiological characteristics are crucial parameters for evaluating the mechanisms of chemical tolerance and associated fitness costs.
Assuntos
Carbamatos , Daphnia magna , Animais , Daphnia magna/efeitos dos fármacos , Daphnia magna/fisiologia , Pirimidinas , Poluentes Químicos da Água/toxicidadeRESUMO
We performed multigenerational tests to clarify the chemical tolerance mechanisms of a nontarget aquatic organism, Daphnia magna. We continuously exposed D. magna to a carbamate insecticide (pirimicarb) at lethal or sublethal concentrations (0, 3.8, 7.5, and 15 µg/L) for 15 generations (F0-F14). We then determined the 48 h-EC50 values and mRNA expression levels of acetylcholinesterase, glutathione S-transferase, and ATP (Adenosine triphosphate)-binding cassette transporter (ABCt) in neonates (<24 h old) from F0, F4, F9, and F14. To ascertain the effects of DNA methylation on pirimicarb sensitivity, we measured 5-methylcytosine levels (DNA methylation levels) in neonates of parents in the last generation (F14). In addition, we cultured groups exposed to 0 and 7.5 µg/L (the latter of which acquired chemical tolerance to pirimicarb) with or without 5-azacytidine (de-methylating agent) and determined methylation levels and 48 h-EC50 values in neonates (<24 h old) from the treated parents. The EC50 values (30.3-31.6 µg/L) in F14 of the 7.5 and 15 µg/L groups were approximately two times higher than that in the control (16.0 µg/L). A linear mixed model analysis showed that EC50 and ABCt mRNA levels were significantly increased with generational alterations; further analysis showed that the ABCt mRNA level was positively related to the EC50 . Therefore, ABCt may be associated with altered pirimicarb sensitivity. In addition, the EC50 value and DNA methylation levels in pirimicarb-tolerant clones decreased after exposure to 5-azacytidine, suggesting that DNA methylation contributes to chemical tolerance. These findings improved our knowledge regarding the acquisition of chemical tolerance in aquatic organisms.
Assuntos
Carbamatos , Cladocera , Pirimidinas , Poluentes Químicos da Água , Animais , Cladocera/metabolismo , Daphnia magna , Daphnia/genética , Daphnia/metabolismo , Acetilcolinesterase/metabolismo , Metilação de DNA , Transportadores de Cassetes de Ligação de ATP/metabolismo , Poluentes Químicos da Água/metabolismo , Organismos Aquáticos , Azacitidina/toxicidade , Azacitidina/metabolismo , RNA Mensageiro/metabolismoRESUMO
To determine the potential effects of pesticides on aquatic organisms inhabiting a realistic environment, we explored the characteristics and mechanisms of chemical tolerance in Scapholeberis kingi(Cladocera). We established a chemical-tolerant population via continuous exposure to pirimicarb, an acetylcholinesterase (AChE) inhibitor, and examined the effects of pirimicarb concentration on the intrinsic growth rates (r) of tolerant cladocerans. We also explored the association between r and feeding rate and tested the involvement of antioxidant enzymes [peroxidase (PO) and superoxide dismutase] and AChE in pirimicarb sensitivity. S. kingi was continuously exposed to lethal and sublethal pirimicarb concentrations (0, 2.5, 5, and 10 µg/L) for 15 generations, and changes (half maximal effective concentration at 48 h, 48 h-EC50) in chemical sensitivity were investigated. In the F14 generation, the sensitivity of the 10 µg/L group was three times lower than that of the control group, suggesting the acquisition of chemical tolerance. Moreover, r was significantly and negatively correlated with 48 h-EC50, suggesting a fitness cost for tolerance. Surprisingly, there was no significant correlation between r and feeding rate. There was a weak but significant positive correlation between each enzyme activity and the 48 h-EC50 value (p < 0.05). Thus, oxidative stress regulation and enhanced AChE may be involved in the acquisition of chemical tolerance in cladocerans. These findings will help elucidate the characteristics and mechanisms of chemical tolerance in aquatic organisms.
Assuntos
Cladocera , Praguicidas , Poluentes Químicos da Água , Acetilcolinesterase , Animais , Inibidores da Colinesterase/farmacologia , Praguicidas/farmacologia , Poluentes Químicos da Água/farmacologiaRESUMO
To ascertain the tolerance mechanisms of aquatic organisms to artificial chemicals, intergenerational sensitivity changes of Chironomus yoshimatsui to a carbamate pesticide (pirimicarb) and pharmaceutical chemical (diazepam) were investigated. The larvae (<48-h-old) in each generation were exposed to both chemicals for 48 h and then the surviving chironomids were cultured until the fifth generation (F0-F4) without chemical addition. The 48-h 50% effective concentration (EC50) value of chironomids was determined for each generation. In the pirimicarb treatment group, the EC50 values significantly increased in F3 and F4, and those in the diazepam treatment group slightly increased. Catalase, Cytochrome P450 and hemoglobin (Hb) mRNA levels were monitored to see whether these were related to the trans-generational sensitivity. Although the generalized linear model results showed that the sensitivity to diazepam was slightly increased in the diazepam treatment, we could not find any mRNA levels related to sensitivity alteration. In contrast, the model approach showed that the chironomids exposed to pirimicarb trans-generationally became tolerant with increasing Hb mRNA levels. Therefore, they might decrease their chemical stress by modifying Hb gene transcription.
Assuntos
Chironomidae , Preparações Farmacêuticas , Poluentes Químicos da Água , Animais , Carbamatos/toxicidade , Catalase , Chironomidae/genética , Sistema Enzimático do Citocromo P-450/genética , Hemoglobinas/genética , Larva , Transcrição Gênica , Poluentes Químicos da Água/toxicidadeRESUMO
We evaluated the real effects of pollutants through a multi-generation study. We tested whether short-term exposure (48 h) of successive (first and second) generations of Chironomus yoshimatsui neonates (<24-h-old) to two acetylcholinesterase inhibitor insecticides, pyraclofos, and pirimicarb, would change insecticide sensitivity and life-cycle parameters over four generations. Additionally, we tested whether acetylcholinesterase (AChE) activity levels would be associated with this sensitivity change. Sensitivities (48 h EC50 value, using immobility as the endpoint) in chironomids (<24-h-old) and insect life-cycle parameters (the number of larvae per egg mass and adult size) were investigated. Parental chironomids produced larvae that were less sensitive than those in the control group following the two 48 h pirimicarb exposure events, whereas exposure to pyraclofos did not affect sensitivity. The AChE activity in larvae with low sensitivity to pirimicarb was significantly higher than that in the control. Thus, increased AChE activity might be associated with low sensitivity. The life-cycle parameters in chironomids recovered from the effects of pyraclofos and pirimicarb suggested they could adapt to the insecticides by changing biomass allocation. Our study suggested potential chemical risks of insecticide stress and how aquatic organisms adapt to it.
Assuntos
Carbamatos/toxicidade , Chironomidae/efeitos dos fármacos , Inibidores da Colinesterase/toxicidade , Inseticidas/toxicidade , Organotiofosfatos/toxicidade , Pirimidinas/toxicidade , Adaptação Biológica/efeitos dos fármacos , Animais , Chironomidae/fisiologia , Ecotoxicologia/métodos , Larva/efeitos dos fármacos , Poluentes Químicos da Água/toxicidadeRESUMO
It has been reported that endogenous or exogenous estrogens can affect the immune system, resulting in immune disorders; however, their direct involvement in such conditions remains to be demonstrated. The purpose of this study was to investigate whether estrogen receptors (ER) are directly implicated in pro-pruritic and pro-inflammatory reactions in cutaneous allergy. Initially, enhancement of the pro-inflammatory response by several ER agonists [methoxychlor (MXC), ß-estradiol (E2), propylpyrazoletriol (PPT; an ERα agonist), and diarylpropionitrile (DPN; an ERß agonist)] was examined in vivo using a male BALB/c mouse model of allergic dermatitis induced by toluene-2,4-diisocyanate administration. The ear swelling response, itch response, and local cytokine secretion were measured. Subsequently, the mechanism underlying the development of such allergic reactions was analyzed in vitro using human epidermal keratinocytes, murine bone marrow-derived dendritic cells (mBMDCs), and the mixed leucocyte reaction assay. Activated cells were exposed to each ER agonist for 24â¯h, and cytokine secretion and cell proliferation were measured. Our in vivo experiments indicated significant upregulation of pro-inflammatory and pro-pruritic responses in the E2-, MXC-, and PPT-treated groups compared to the control group; however, no change was observed in the DPN-treated group. Levels of cytokines expressed by keratinocytes, such as TSLP and IL-33, were particularly increased by exposure to E2, MXC, or PPT. These in vivo results were confirmed in vitro in keratinocytes, but not mBMDCs or T cells. Our findings imply that ERα is involved in pro-inflammatory and pro-pruritic responses in cutaneous allergy through activation of keratinocytes.
Assuntos
Dermatite Alérgica de Contato/tratamento farmacológico , Moduladores de Receptor Estrogênico/uso terapêutico , Receptor alfa de Estrogênio/efeitos dos fármacos , Inflamação/tratamento farmacológico , Prurido/tratamento farmacológico , Animais , Proliferação de Células/efeitos dos fármacos , Citocinas/metabolismo , Células Dendríticas , Dermatite Alérgica de Contato/patologia , Orelha Externa/patologia , Feminino , Humanos , Inflamação/patologia , Queratinócitos/metabolismo , Teste de Cultura Mista de Linfócitos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Prurido/patologiaRESUMO
Bisphenol A (BPA) is used in various areas of daily life as a major component of plastic products. However, it is also known as a strong endocrine disruptor that affects the human immune system. Studies have indicated that BPA possibly exacerbates allergic diseases such as atopic dermatitis and asthma. The main aim of this study was to elucidate whether BPA is directly involved in the exacerbation of allergic inflammation. Initially, in vivo experiments with mouse models of allergic inflammation induced by Th2 type hapten toluene-2, 4-diisocyanate (TDI) was performed. Mice were subjected to oral administration of BPA 48, 24, and 4 h before challenge with TDI. Dermal challenge of TDI onto the ear auricle was performed for the allergic dermatitis model, and intratracheal challenge of TDI was performed for the allergic airway inflammation model. In the allergic dermatitis model, ear-swelling response was significantly downregulated by high doses of BPA. The opposite reaction was observed in the allergic airway inflammation model, including significant exacerbation of red coloration in the lung, local cytokine levels, and total IgE levels in serum by BPA administration. To confirm the in vivo results, in vitro experiments with human epidermal keratinocytes (HEKs) and bronchial epithelial (BEAS-2B) cells were carried out. Significant enhancement of cytokine release from BEAS-2B cells but not HEKs in the BPA-treated group supported the in vivo observations. Our results imply that exposure to BPA directly exacerbates allergic airway inflammation but not allergic dermatitis.